Modern vehicles are typically configured as either two- or all-wheel drive. Either type of a vehicle may employ a conventional powertrain, where a single engine is used to propel the vehicle, or a hybrid powertrain, where two or more distinct power sources, such as an internal combustion engine and an electric motor, are used to accomplish the same task. Furthermore, a multi-speed automatically-shiftable transmission may be employed as part of either type of a powertrain, and may thus be used in a hybrid vehicle with all-wheel drive.
In order to maximize fuel efficiency of a hybrid powertrain, the vehicle's engine may be shut off when engine torque is not required for driving the vehicle. Such a situation may be encountered when the hybrid vehicle is maintaining a steady cruising speed, is in a coast down mode, i.e., when the vehicle is decelerating from elevated speeds, or is stopped.
An all-wheel drive hybrid vehicle may be configured as an axle-split vehicle. In such a vehicle, an electric motor is set up to power one vehicle axle and the engine is configured to power the vehicle's remaining axle(s), thus generating an on demand electric all-wheel drive. In such an axle-split hybrid vehicle, the electric motor may be capable of propelling the vehicle while the transmission is in neutral and the engine is shut off. However, in the event the engine needs to be restarted to participate in driving such a vehicle, the resumed application of engine torque through the transmission while the vehicle is in motion may generate an unwanted driveline disturbance.